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Biomedical subjects

G Diaz

Publications and source records attributed to G Diaz.

At least 73 records · Page 4Linked to original sources
PubMed1990

Copper distribution within and between newborn livers.

Copper concentration was determined in different liver samples (blocks, needle biopsy and bile) obtained from 9 newborns and 3 infants at autopsy. Tissue blocks, sampled at ten equally spaced intervals between the left and the right lobe, revealed in newborns high copper concentrations, ranging from 93 to 335 mg/Kg of dry tissue with an upward trend from the right to the left lobe. The situation differed in infants where a lower and more evenly distributed copper content, ranging from 49 to 123 mg/Kg of dry tissue, was found, which seemed to approximate the situation found in adults. Copper concentration was generally high in bile, with an overall range from 99 to 413 mg/Kg of dry material. This fact was particularly significant in infants, considering their low hepatic copper content. Copper content determined in percutaneous biopts was significantly correlated to (P less than 0.01), though only moderately predictive of (r2 = 0.54), the average copper content calculated from the ten liver blocks.

Bile↗
PubMed1989

Elliptic fourier analysis of cell and nuclear shapes.

The elliptic Fourier analysis (EFA) is proposed to characterize the cell and nuclear shape. The principal feature of this method is that it decomposes shapes with a closed contour into subshapes each of which maintains a closed contour. A set of homogeneous, nonredundant descriptors, independent of the contour rotation and translation, is computed from the elliptic Fourier coefficients. These descriptors also account for the contour size and resolution. The paired analysis of the cell and nuclear shape provides an exhaustive and accurate definition of the nucleoplasmic configuration.

Computer Simulation↗
PubMed1989

Active reduced-size hexapeptide analogues of luteinizing hormone-releasing hormone.

A series of reduced-size hexapeptide analogues of LH-RH were synthesized that contain the residues corresponding to amino acid positions 4-9 and are linked to various carboxylic acids in place of residue 3. These compounds were tested in vitro in the rat pituitary receptor binding and LH release assays. A wide range of binding affinities was obtained up to and exceeding that of LH-RH. Both agonists and antagonists were obtained. From the SAR studies, it appears that a very precise size, length, and shape of the substituent at position 3 is required to achieve agonist activity, whereas the structural requirements for antagonist activity appear to be much less stringent. Depending on the nature of the substituent at positions 6 and 4, the biological response switches from antagonist to agonist or vice versa. The results suggest that conformational changes at position 6 or 4 feed back to the substituent at position 3, which induces the change from agonist to antagonist. The most potent compounds in the series were tested in vivo and found to be active.

Animals↗
PubMed1987

Quantitative ultrastructural approach to the study of the spatial relationships among cell organelles. I. Cytological organization of human exocrine epithelia.

Currently available morphometric methods provide useful information on the three-dimensional properties (such as volume, surface, etc.) of biological structures. These methods, however, do not reveal how the same structures are spatially organized within the cell. A sum of problems, which concern mainly the definition of shape and location of the sectioned structures, does not allow the three-dimensional representation of the organelle arrangement from a quantitative analysis of sections. Following a different approach, this study considers the topographic relationship between ten distinct subcellular structures: nucleus, Golgi, ribosomes, mitochondria, lysosomes, lipid droplets, secretory granules, and apical, lateral, and basal plasmalemma. The analysis of associations from 2 X 2 tables calculated for each pair of structures and the pattern of multiple associations obtained by clustering methods provide a useful description of the spatial relationship among different cell compartments. The results of the investigation carried out in parallel on seven human exocrine glands (pancreas, parotid gland, submandibular gland, lacrimal gland, ceruminous gland, ampulla of the vas deferens, and seminal vesicle) allow an immediate evaluation of the method and a comparative analysis of the cytologic organization of secreting cells of human exocrine glands.

Data Interpretation, Statistical↗
PubMed1986

Nonrandom distribution of coated pits and vesicles in the connective tissue cells of the trabecular meshwork of rabbit.

Coated pits (CPs) and coated vesicles (CVs) are distributed nonrandomly along the surface of the connective tissue cells of the rabbit trabecular meshwork. Morphometric and statistical analyses of the distances between consecutive structures reveal a tendency to cluster, which is apparently higher among CVs than among CPs. The spatial relationship between CVs and CPs is also demonstrated by the analysis of their association (presence/absence) in each cell. The data suggest the hypothesis that each cluster is formed by structures in the same stage of maturation. In addition to the recent demonstration of the clustering of CPs in transformed cells in vitro (Pfeiffer et al. 1980), our findings indicate that: (a) clustering is characteristic of both CVs and CPs; (b) it also occurs in normal tissue cells; (c) it represents a further peculiarity, which confirms the specific nature of receptor-mediated endocytosis; (d) it reflects, at a higher level, the clustering of the receptor molecules, which are responsible for the high selectivity of the endocytic process.

Animals↗
PubMed1984

Left ventricular function in chronic anemia: evidence of noncatecholamine positive inotropic factor in the serum.

The enhanced left ventricular (LV) performance observed in anemia has been attributed to changes in preload and afterload. Whether there is a concomitant increase in contractility is controversial. Seventeen patients with chronic anemia (hematocrit range 17 to 30%) and 17 control subjects, matched by age and sex, were studied. In 10 patients and 10 control subjects (group I), a noninvasive evaluation of LV function through M-mode echocardiography and cuff blood pressure recording was performed. In patients with anemia, stroke volume increased 43% (p less than 0.01), fractional shortening 21% (p less than 0.001), and mean rate of circumferential shortening 32% (p less than 0.001). In patients with anemia, end-systolic stress decrease 27% (p less than 0.05) and diastolic blood pressure 21% (p less than 0.001). The effect of serum from these patients and control subjects on the development of isometric tension by isolated cat papillary muscles was assessed compared with the basal (Ringer-Locke bath) values. Anemia serum increased maximal developed tension 21% and maximal rate of tension development 20% relative to basal levels. These changes were significantly higher (p less than 0.001) than the increases produced by control serum (8% and 7%, respectively). In the 7 patients with anemia in group II and their matched controls, the in vitro isometric tension characteristics were assessed before and after blocking beta adrenoreceptors with propranolol, 10(-6) M. The observed increase in the developed tension persisted after beta blockade, as well as the enhancement of the maximal rate of tension development. Plasma catecholamine levels in this group II were within the normal range.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Stereomorphological arrangement of capillaries in skeletal muscle in normal and stenosed young and adult rats.

The stereomorphological arrangement of skeletal muscle capillaries depends on many factors. Genetic biochemical composition of muscle fibers, age, and training can interfere with the growth of the capillary network. This study is focused on the age effect of chronic reduction of blood flow, as in arterial stenosis, in skeletal muscle network of young rats when compared with adult rats. It has been observed that there is a statistically significant decrease of the length of short capillaries which cross the muscle fibers. In adult rats the opposite occurs.

Age Factors↗
PubMed1984

Shear viscosity of the surfactant from dog lungs.

Surface viscosity (eta S) was measured in the pulmonary lavage fluid obtained from 40 mongrel dogs. Two experimental methods were employed to determine surface viscosity: a) Fourt's "torsion pendulum" procedure; and b) the "viscous traction" viscosimeter. A satisfactory correlation (r = 0.88) between these two methods was obtained. The mean value for surface viscosity of the pulmonary lavage fluid was 3.8 X 10(-2) surface-poise (s.p.) with the torsion pendulum procedure, and 4.3 X 10(-2) s.p. with the viscous traction viscosimeter. The implications of surface viscosity in pulmonary mechanics is discussed, as well as the effects of blood plasma addition to the pulmonary lavage fluid. A significant increase of surface viscosity could be observed when blood plasma was added to the hypophase, in concentrations greater than 0.1%. This increase in surface viscosity might be of importance when related to the augmented respiratory work during the evolution of pulmonary edema.

Animals↗
PubMed1983

Left-hand advantage in right-handers for spatial constant error: preliminary evidence in a unimanual ballistic aimed movement.

While the superiority of the right hemisphere for the processing of spatial relationships in normal right-handers has been largely accepted, it is surprising that evidence for an advantage of the left "nondominant" hand over the right "dominant" hand in spatial motor tasks is up to now almost totally lacking. We report preliminary evidence that normal right-handers perform open-loop ballistic aimed movements with a smaller constant error when using the left rather than the right hand. In addition, constant error is found to be minimal for movements directed toward the left half-field.

Functional Laterality↗
PubMed1983

Supercoiling of 30-nm chromatin fibers around a nuclear axis in human retinal pigment cell nuclei: electron microscope evidence for a chromatin macrostructure.

Nucleosomes and higher-order chromatin structures have been identified in the range of resolution of 10-30 nm. No information is available on higher configurations that involve chromatin arrangements at the nuclear level. Thin sections of human retinal pigment cell nuclei reveal an orderly array of 30-nm chromatin fibers on the inner nuclear surface. The observations can be three-dimensionally explained by a coiled or a serially circular arrangement of fibers around a central axis of the nucleus. The axial chromatin orientation shows no apparent relationship to the epithelial cell polarity nor to the irregular shape of the nuclei. The described configuration, which is compatible with a chromatin structure of third order, represents the first example of chromatin architecture coherently organized at the nuclear level.

Cell Nucleus↗
PubMed1982

Coated pits and coated vesicles in the endothelial cells of trabecular meshwork.

Coated pits (CPs) and coated vesicles (CVs) were investigated in the trabecular meshwork of man and rabbit. In both man and rabbit CPs and CVs appear to be randomly distributed throughout the trabecular tissue. CVs are located in the peripheral cytoplasm of the trabecular endothelial cells and show an average diameter of 0 . 16 micron. The ratio between the number of CPs and CVs ranges from 0 . 53 (rabbit) to 0 . 6 (man). The number of CPs and CVs is higher in rabbit than in man. Consequently, the overall CPs surface and CVs volume density estimates are higher in rabbits, where CPs represent about 1% of the cell surface and CVs account for about 0 . 4% of the cell cytoplasm. In man these percentages are 0 . 46 and 0 . 17%, respectively. No significant changes of CPs and CVs were found in rabbits with corticosteroid-induced ocular hypertension. However, changes in length of boundary membrane of CPs, though not statistically significant, were accompanied by proportional changes in CVs diameter.

Animals↗
PubMed1982

Quantitative ultrastructural study of the anterior chamber angle of the rabbit with corticosteroid-induced ocular hypertension. Stereology of the rabbit angle.

The ultrastructure of the trabecular meshwork of the anterior chamber angle after corticosteroid-induced hypertension was studied with TEM. A morphometric analysis by means of stereological techniques did not reveal changes in the trabecular meshwork of the treated eyes. A preliminary stereological investigation of the inner wall of the aqueous plexus was carried out with a computer-assisted device.

Animals↗